UPS

I was given an American Power Conversion 450 AT+ UPS. No manual and couldn't find one on the APC site. Said to be faulty.

It works but doesn't seem to work when power cuts off.

Unit has two switches on the front. The first is an ALARM rocker switch which when toggled off tests the alarm system. Shrieking sound. Toggling on disables the alarm. This switch only functions when the SECOND switch is OFF.

The second switch is labelled OUTPUT POWER and when in the OFF posiition glows red. In this position anything plugged into the UPS gets power. When it is in the ON position no power goes to any connected device and the red light on it is off.

Now is this the normal mode of operations as I have described for this unit?

Should battery power be getting to this unit when the OUTPUT POWER switch is in the on condition?

If i dsconnect the power to the UPS unit at the wall, any device plugged into the UPS dies an instant death. Shouldn't the UPS be supplying power to this device? The alarm system cuts in though and sounds a high pitched shriek.

I suspect that the battery system for this unit is not charged fully. How can I recharge it fully because I suspect it may be a NIcad pack of some sort not charging fully. Some sort of memory effect.

I wonder if the fuse (APC usually solders them in) has blown. I would pop the cover and see if there isn't an automotive type fuse blown.
Here is a link to the manuals for APC, if you haven't already been there

Diagram inside indicated three. Found three but not qute where the diagram said, one small one soldered, one mother-of-all fuses in clips. One external fuse at back under screw cap. Fuses looked all OK.

Been to that site and nothing there. This beastie is old, about 10 years I think.

Some UPS units use lead-acid batteries. If they have been standing idle they may have discharged and the electrodes have degraded (sulfation). A long-time trickle charge MAY restore some power, but you'd probably have to use an external charger, as the voltage from the cells will be high enough to fool the standard charger to think the battery is full. This requires some knowledge about charging sealed lead-acid batteries.

If it has a NiCd pack you may be able to cycle the battery; again an external charger may be better.

Your batteries need replacing most likely. I have a UPS that's about 3 years old and has the same symptoms. Your unit is considerably older and the likelyhood that the batteries need replacing is quite high.

the general consensus here seems to be dead batteries.
I agree with that!
thought you might try batteries plus, they're local to most cities nation wide (USA), and local is better since batteries are heavy, and would be expenive to ship.

Thought they were NiCds. On checking they were SLA batteries. Never pulled a UPS apart before and thought they used NiCds.

Comment on charging forced me to do some searching on information on SLAs. Yes, interesting. Measured voltages on batteries and they are down and I think they have had it. Will probably stick an old car battery across and see if it works that way. If it does then may consider updating the old batteries. But the project is on hold for the next month.

Memory got jogged and I remember seeing a server room setup where the UPS on a NEC small mainframe system seemed to be a standard UPS that used a car battery to supply the power. May have been jury rigged to run that way.

Just about any 12V lead-acid battery will work in these applications. Most UPSs use "gel-cell" type but automitive or "motorcycle" types, especially the SEALED kind work find. If you don't need the enclosure closed or can run a cable to an external battery, that is fine.

Be sure, however to:

1) Never turn a non-GEL type lead-acid battery on its side or top. It WILL make a MESS!!!

2) Be sure you have ventilation for non-sealed types to prevent any accumulation of explosive hydrogen gas which is vented in normal operation.

3) If you run a wire, be SURE you use one of sufficient gauge or you will have a fire danger. Calculate the max current like:

Imax = (UPS_OUTPUT_POWER/BATTERY_VOLTAGE) / CONVERSION_EFFICIENCY

So your 450 VA UPS (assuming a conversion efficiency of 75% would need to carry:

Imax = (450/12) / 0.75 = 50 Amps

So "zip" cord is out. Something like car battery jumper cables are more in order, good ones are 6 or even 4 AWG. Keep the length short whatever you use.

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